The post-surgical patient and post-trauma patient are prone to intrapulmonary shunt either from regional atelectasis or diffuse alveolar deaeration - so-called post-trauma R.D.S. The initiating cause for regional atelectasis presumably is failure to provide adequate distending force to normal or congested lobes. We propose to study the effect of local distending forces and interdependence on the various portions of lung in baboons, dogs, and sheep. A second set of experiments will study the lymph-plasma ratio of proteins in the lung when hemodilution is induced by electrolyte infusion. These studies will be designed to help answer whether protein free electrolyte or plasma is the better solution for resuscitation from hypovolemic shock. BIBLIOGRAPHIC REFERENCES: Zarins, C. K., C. G. Bayne, C. L. Rice, R. M. Peters, and R. W. Virgilio. Does spontaneous ventilation with IMV protect from PEEP-induced cardiac output depression? J. Surg. Research 22: 299, 1977. Shapiro, A. R., R. W. Virgilio, and R.M. Peters. Interpretation of alveolar-aterial oxygen tension difference. Surg. Gynecol. Obstet. 144: 547, 1977.